proxmox: only install firewall rules on one node

And let the cluster take care of distribution.

roles/proxmox/tasks/firewall.yml

@@ -1,7 +1,3 @@
-- name: Retrieve service list
-  set_fact:
-    services: '{{ query("netbox.netbox.nb_lookup", "clusters", raw_data=true, api_filter="name="+cluster) | map(attribute="custom_fields.services") | flatten }}'
-
 - name: Set up firewall
   template:
     dest: /etc/pve/firewall/cluster.fw
@@ -9,4 +5,4 @@
     mode: 0640
     owner: root
     group: www-data
-
+  when: inventory_hostname == primary